The approach to fitting conventional hearing aids was based on knowledge about how young adults hear relatively simple sounds in ideal environments. In essence, beyond operations such as filtering, amplification, and compression that resemble auditory processing by the cochlea, hearing aids have begun to incorporate more complex operations that emulate aspects of higher-level auditory and cognitive processing such as attention, memory, and language. The new “intelligent” devices respond to ongoing analysis of the presumed signal and the presumed background. The need for user-operated controls is eliminated by such automatic adjustments. Acoustical factors in hearing aid fitting continue to be dominated by the properties of the speech signal that are known to be relevant to intelligibility in quiet however, digital technology has much greater flexibility to adjust automatically to an incoming acoustical signal based on assumptions regarding the dynamic interaction of a target speech signal with simultaneous competing signals. The main personal factor guiding hearing aid fitting continues to be the basic audiometric profile of the individual however, increasingly, other non-audiometric factors may also influence fitting decisions ( Kricos, 2000). In contrast, the fitting of current complex digital signal processing hearing aids can vary according to a wider variety of personal and acoustical factors, and the response of the device can be dynamically altered according to ongoing sampling and analysis of input by the device. In addition to the settings determined by the fitter, conventional hearing aids also had a small number of controls ( e.g., on/off, volume, tone) that could be adjusted by the user according to his or her situation-specific listening preferences. Complex digital signal-processing algorithms now enable fittings that are vastly more variable than would have been possible with analogue technology.Ĭonventional hearing aids had relatively few options ( e.g., gain, output, frequency response) that were set by the fitter based on the audiometric profile of the user following “rules” guided by research on the correspondence between the audibility and the intelligibility of speech. Most hearing aids sold in 1999 were analogue (60%), and relatively few were digital (12%) however, by 2003 the pattern was reversed, with sales of digital hearing aids being the most common (58%) and sales of analogue aids being reduced (26%) ( Fabry, 2003). Over the last decade, there have been landmark advances in the design of hearing aids. The purpose of the present paper is to provide an integrated framework for understanding how auditory and cognitive processing interact when older adults listen, comprehend, and communicate in realistic situations, to review relevant models and findings, and to suggest how new knowledge about age-related changes in audition and cognition may influence future developments in hearing aid fitting and audiologic rehabilitation. Long-standing approaches to rehabilitative audiology should be revitalized to emphasize the important role that training and therapy play in promoting compensatory brain reorganization as older adults acclimatize to new technologies. Specifically, we argue that a synthesis of new knowledge concerning the functional neuroscience of auditory cognition is necessary to inform the design and fitting of digital signal processing in “intelligent” hearing devices, as well as to inform best practices for resituating hearing aid fitting in a broader context of audiologic rehabilitation. The early pioneers of audiology anticipated such a unified view, but today, advances in science and technology make it both possible and necessary. In the present paper, we suggest that these two views can begin to be unified following the example set by the cognitive neuroscience of aging.
A “processing” view based on psychologic functions inspired research to test alternative hypotheses about how lower-level sensory processes and higher-level cognitive processes interact. A “site-of-lesion” view based on anatomic levels inspired research to test competing hypotheses about the contributions of changes at these three levels of the nervous system. Recent advances in research and clinical practice concerning aging and auditory communication have been driven by questions about age-related differences in peripheral hearing, central auditory processing, and cognitive processing.
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